Conda-project

This fix brings some level of backwards compatibility with versions <0.11.0. The `defaults` channel is automatically added to the solve if not present in the anaconda-project.yml file. By adding `nodefaults` this behavior is disabled.

In this release `osx-arm64` and `linux-aarch64` are officially supported. Also, anaconda-project respects the `CONDA_SUBDIR` env var if you need to switch your platform. For example, to prepare an `osx-64` env on an M1 Mac.

An important breaking change is that anaconda-project will only install packages from channels listed in the anaconda-project.yml file and not from channels defined in your .condarc file.

This version drops support for Python 2.7 in the env where anaconda-project is installed. You can still use anaconda-project to make Python 2.7 environments. We just won't be testing anaconda-project in a Python 2.7 Miniconda install.

fixed an issue where downloads with out content-length will fail

Progress bars have been added for

* file downloads during the prepare step
* project download and unarchive

This version improves support for pip packages with the `add-packages`, `remove-packages`, `list-packages`, and `lock` commands.

Secondly, two new options for exporting projects.
* `anaconda-project archive --pack-envs <archive>` will use [conda-pack](https://conda.github.io/conda-pack/) to include full Conda environments in the archive
* `anaconda-project dockerize` will use [s2i-anaconda-project](https://github.com/Anaconda-Platform/s2i-anaconda-project) to build Docker images from your project

See the documentation for more details on how to use these new features.